Until relatively recently, persons who are blind, have low vision or are learning disabled or otherwise print handicapped are denied access and orientation that the general population takes for granted in every day life. Finding their way is a challenging event often ending with asking strangers' help. Whether getting on the right bus, finding a restroom or a telephone, determining directions to elevators or exits, crossing streets or understanding directories in public places, these populations are placed at a great disadvantage and often in danger. Directional "wayfinding" devices have not existed to provide them the ability to "read and see" remote signs, much less utilize interactive signs, automatic teller machines, informational and commercial kiosks, vending machines, and the like. In addition, tourists and other visitors who are not fluent in the local language are often at a similar disadvantage since the relevant printed signs or displays employ a language which is not intelligible to them.
In recent years an information and wayfinding system has been developed for assisting blind, low-visioned and otherwise print-handicapped individuals. The system, marketed under the trademark Talking Signs, consists of single channel infrared transmitters and receivers. Transmitters are placed on key signs in the environment which continually transmit the message of the sign. The receiver is carried by the person who activates it when direction or information is desired.
Under many circumstances, the foregoing system provides excellent results in use. However when used in the presence of an ambient background of light energy such as sunlight, difficulties may be encountered, such as difficulty or, possibly, inability to detect the intended signal. Thus a need exists for a way of nullifying the adverse effect of such background light energy so that detection units can be utilized effectively both in the presence and in the absence of an ambient background of intense light energy such as sunlight. In addition, a need exists for a way to receive signals transmitted at various carrier frequencies, thereby enabling transmission and reception of multiple messages or multiple versions (e.g., different languages) of the same message.
This invention is deemed to fulfill these needs in a highly efficient manner.